The invention relates generally to low thrust rocket engines. More particularly, the invention relates to low power thruster for extremely low temperature applications.
Low thrust monopropellant engines have been employed for many years to satisfy attitude and velocity control requirements for satellites. The conventional thruster employes a catalytic bed to ignite the propellant. The use of a catalytic bed in the thruster requires the almost exclusive use of hydrazine as a propellant. Hydrazine (N.sub.2 H.sub.4) contains no carbon atoms and consequently will not degrade the catalyst bed which may be, for example, Shell 405. The use of hydrazine, however, may cause problems with the propellant supply system because of its high freezing point which raises the danger of the thruster propellant freezing when the satellite is in outer space. An attempt to substitute low freezing point propellants with otherwise similar characteristics to hydrazine has been made with the catalyst bed thrusters but such propellants have degraded the catalyst bed because they are universally carbonaceous and combustion has resulted in carbon deposits on the catalyst bed. This action substantially lowers the useful life of the thruster.